The present invention relates to a pushing device and to a vehicle for receiving installation or paving material, particularly a road paver or feeder vehicle
During the installation of pavements, a heavy goods vehicle (HGV) loads road pavers or feeders with the material that is to be installed. The material is thereby tipped by the HGV directly into the hopper of the road paver or of the feeder.
To transfer the material, a loaded HGV slowly drives backwards to the vehicle that is to be loaded, stops a short distance away from the vehicle and waits until the approaching paver or feeder is docked to the chassis of the HGV by means of a pushing device. In most cases, the pushing device docks to the rear tires of the HGV. After the docking process, the road paver or feeder accelerates the HGV from a standing position to the installation speed and pushes said HGV in front of itself until such a time as the HGV has been fully unloaded.
The docking to the road paver or the feeder, and also the drive together along the installation route, while the material is being dumped into the hopper greatly depend on the routine of the HGV driver. In this situation, however, it frequently happens that serious installation mistakes are made because the HGV driver applies the brakes of the HGV for too long and/or with too much force. This can lead to a delayed drive of the pushing vehicle, as a result of which installation errors occur in the pavement. Pushing the HGV also squanders energy in order to maintain the installation speed.
On the other hand, the HGV driver is not permitted to release the brake of the HGV completely, because otherwise the HGV would be pushed away towards the front due to the effect of the momentum of the material sliding out. Consequently, the material that slides out would no longer land in the hopper of the road paver or feeder and would instead fall in front of the vehicle.
For this reason, an HGV driver should be able to balance the braking force on the HGV sensitively against the push of the road paver or feeder so that no damage results in the pavement and so that the road-building material lands on target in the hopper.
In a further situation with regard to the material transfer, the HGV does not remain in front of the road paver or feeder, and instead slowly drives backwards against a pushing device of the respective vehicle. It is important thereby that the HGV does not collide against the road paver or feeder in an abrupt manner, which would namely result in the vehicle that is to be supplied being displaced in a jerky manner in a direction opposite to the installation direction, which would lead to damage in the new roadway surface. The HGV that is driving backwards must therefore be delayed until it comes to a standstill by means of a pushing device. It is also important thereby that the HGV is driven against the pushing device of the road paver or feeder with a great deal of routine. There is a risk, however, that the HGV collides against the pushing device too quickly, or that the HGV driver drives against the pushing device for too long, which can lead to a displacement of the paver and in this way to unwanted line-shaped imprints in the roadway surface.
Most of the known pushing devices are bars in a floating mount with push rollers on the ends, whereby the pushing devices are rigidly connected to the paver frame. In some cases, the bars can also be manually or automatically adjusted in the driving direction. When the push rollers dock against the HGV tires, the HGV tires deform elastically and thereby store deformation energy. Even in the case of small acceleration paths or brake paths, the acceleration levels rise strongly, as do consequently the dynamic forces between the HGV and the paver or feeder. The success of the drive or braking procedure is also thereby very strongly dependent on the skill of the HGV driver. For this reason, there is often someone giving directions in front of the road paver in order to support the HGV driver in the docking.
Also known are pushing devices which support the push rollers individually or in groups by means of coil springs or hydraulic cylinders. Such alternatives have greater movement possibilities for the pushing device especially during docking. Pushing devices with coil springs, however, have the disadvantage that as a result of the deformation, they store energy that would tend to accelerate the HGV away from the paver again after the docking. This can happen in a jerky manner, as a result of which the emptied, lighter HGV again loses contact with the road paver or feeder. During renewed docking, it is thereby possible that damage results to the pavement.
In contrast, hydraulic systems have greater flexibility with respect to absorption and spring characteristics. In these cases, however, the high level of complexity is disadvantageous, whereby there is also additional energy consumption in the case of actively controlled hydraulic systems.
U.S. Pat. No. 5,100,277 A describes a material transfer system for a road paver. A road paver, a material-supplying HGV and a feeder arranged between the road paver and the HGV are provided for the material transfer system. The material-supplying HGV is thereby docked against a hydraulic advancing device of the feeder vehicle in order subsequently to unload material. The hydraulic pushing device can be controlled by a hydraulic pump.
DE 920 39 02 U1 refers to a road construction vehicle with an extendible support unit. From the driver's cabin, it is possible to use the extendible support unit to regulate the distance between the road construction vehicle and a transport vehicle that is being pushed at the front.
DE 94 08 192 U1 describes a road paver with a storage container and push rollers that are attached to a cross-arm with mountings and that are arranged in front of the storage container.
U.S. Pat. No. 5,004,394 A describes a pushing device that is arranged on a road paver vehicle or on a feeder, whereby the pushing device is mounted on a cross-arm in a resilient manner by means of springs or hydraulic cylinders.
DE 92 038 67 U1 refers to a pushing device for a road construction vehicle, whereby the pushing device comprises adjustable ejector rollers that can be extended crosswise with respect to the driving direction in order to change the width of the pushing device.
DE 195 13 323 A1 describes a road paver with one or more coaxial push rollers that are mounted in a rotatable manner by means of a pendulum cross-arm.
EP 2 295 641 A2 describes a construction machine with push rollers mounted on the chassis and supported by hydraulic cylinders. A pressure limiting valve is provided in order to cushion the push rollers when an HGV collides into them. This, however, has the technical disadvantage that the pressure limiting valve remains closed up to a certain pressure rise and as a result stores energy, which can lead to an agitated pushing of the HGV. In addition, it is difficult to regulate the speed of the paver at the moment at which the pressure limiting valve opens.
U.S. Pat. No. 4,955,754 A describes a pushing device for a road paver that comprises a hydraulically activated cushioning device with a floating mounting. An HGV that is driving backwards can be cushioned with the hydraulically activated cushioning device.
DE 198 21 090 A1 relates to a road paver vehicle with a pendulum cross-arm, whereby a feeder vehicle driving backwards towards a half of a bucket of the road paver vehicle comes into contact with the respective pendulum cross-arm, at which point the feeding can begin.
DE 35 24 463 A1 describes a vehicle for the continuous feeding of a road paver, whereby the vehicle comprises support rollers against which an unloading supply vehicle can dock with its rear wheels.
DE 36 12 131 A1 describes a road surface paver with push rollers that press against rear vehicle wheels of a heavy goods vehicle when this loads the road surface paver with a mixture.
CN 200520051281.X relates to a pushing device that is mounted to a road construction vehicle, whereby the pushing device comprises a cushioning mechanism with coil springs.